MxCsr - "A callee that modifies any of the non-volatile fields within
MxCsr must restore them before returning to its caller. Furthermore, a caller
that has modified any of these fields must restore them to their standard
values before invoking a callee ..." [5].

FpCsr - "A callee that modifies any of the fields within FpCsr must
restore them before returning to its caller. Furthermore, a caller that has
modified any of these fields must restore them to their standard values before
invoking a callee ..." [6].

"The MMX and floating-point stack registers (MM0-MM7/ST0-ST7) are preserved
across context switches. There is no explicit calling convention for these
registers." [7].

"The 64-bit Microsoft compiler does not use ST(0)-ST(7)/MM0-MM7".
[8].

"The control bits of the MxCsr register are callee-saved (preserved
across calls), while the status bits are caller-saved (not preserved). The
x87 status word register is caller-saved, whereas the x87 control word (FpCsr)
is callee-saved." [10].